Electric heater



Patented Aug. l1, 1925.

UNITED STATES JAMES C. DONELAN, GF SPRINGFIELD, ILLINOIS.

ELECTRIC HEATER.

Application filed November 11, 1924.

To all whomz't may concern.'

Be it known that l, Jarras. C. ONELAN, citizen of the United States, residing at ate of Illinois, have invented a new and seful Electric Heater, of which the followng is a specification.

This invention relates primarily to relatively small heaters such as are used by dentists in laboratory work or such as are used my manufacturers of small articles which may be advantageously treated in portable heaters of the type described.

The purposes of the invention are to providea light and easily portable heater which may be used in connection with the usual lamp-sockets of an electric lighting system; to provide a heater having relatively high heating value considering the size of the heater; to provide a heater having a conw tinuous electric resistance element ext-end ing the full length of the heating chamber' and entirely around its inner wall; to pro vide simple and effective means to facilitate the insertion of resistance element in the heater; to provide means preventing accident-al displacement of the resistance coil; to provide a heating chamber adapted to receive and hold upright, either cylindrical crucibles, or polygonal crucibles; or containers; containing the articles to be treated; and to provide improved means for electrically connecting the heater with a lampsocket of usual construction.

With these ends in view my invention consists in the novel features of construction a. combination of parts shown in the accompanying drawing to which reference is hereby made; and now to be described and finally recited in the claims.

The invention is illustrated in the accompanying drawing in which Figure 1 is a front elevation of an electric heater embodying my invention. Fig. 2 is a top view and Fig. 3 is a bottom view of the same heater. Fig. 4 is a vertical section through the heater taken on the line 4 4 of Fig. 1. Fig. 5 is a reduced developed plan partly in section, showing the continuous resistance coil in place in the inner wall of the heater. Fig. 6 is a top view of the de velopcd circular wall of the heater. Fig. 7 is a perspective view of the screw threaded metal sleevev which surrounds the reduced cylindrical part of the heater and engages in Serial No. 749,197.

the lamp-socket; and Fig. 8 is an enlarged perspective view of one contact plate. The same reference numerals designate .the same parts in all the views.

'lhe heater body l0 is preferably of porcelain or iire-clay, or other heat-resisting and insulating material, and has a reduced cylindrical extension 12. The intermediate part 13 of the body is beveled or tapered as shown. The part 12 has an integral downwardly extending neck 14, the purpose of which will be explained later. A series of dove-tail vertical grooves 15 are formed in the inner wall of the heater. At the lower. end of each vertical groove is a corresponding hole 16 extending downwardly through the beveled part 13. Vertical columns 17 integral with the wall of the heater, separate the grooves 15. The upper ends of the columns 17 are rounded as shown at 18 to facilitate the inserting of a continuous coil 19 in the grooves and across the upper ends of the columns.

To place the resistance coil 19 in the heater, one end of the coil will be inserted in one of the openings 1.5, the coil will then be pushed upward in the corresponding dove-tail groove and will be carried across the rounded upper end 18 of the column 17 and then downward through the next groove; and so on until the resistance coil occupies all the grooves. The inclined walls of the dove-tail grooves will prevent the resistance coil from being accidentally detachedand falling into the heater.

A number of the columns 17 in the present instance four have vertical grooves, 20 one in each column. rl`he grooves 20 are in such relation to each that the vert-ical edges of a polygonal Crucible or container indicated by dotted lines 21 may engage in the grooves and hold the Crucible or container against rotation in the heater.

The neck 14 has a flat part 22 and a central bore23. The bore 23 extends upwardly through the neck and into an enlarged counter-bore 24 in the part 13. A metal screw threaded sleeve 26 is partially closed at one end leaving an opening 27 toreceive the terminal members of the neck 14. The wall 28 of the sleeve engages on the shoulder 22 of the neck to prevent rotation of the sleeve on the neck. A contact plate 29 is riveted on the inside of the sleeve.

A screw threaded socket 37 of usual construction, electrically connected with any suitable source of electric supply, receives the screw-threaded sleeve 2G to connect it electrically with the source of supply and to support the heater in an upright position convenient for use.

To assemble the parts; the electric resistance element 19 will be placed in the retaining grooves in the inner wall et the heater body as already described; the contact plate 31 will be inserted in the radial way 30 with the hole 38 in the plate in line with the bore 23 in the extension 12; and the outer terminal part Sil olf the plate will be connected with one terminal or the coil 19 by the binding screw 36; the screw threaded sleeve 2G will be placed cn the er:- tension 12 with the neck 14e in the opening 27 and the wall 28 of the sleeve against the shoulder 22 ot the neck, to prevent rotation ot the sleeve relative to the extension 12; the screw 32 will be inserted in the bore and will be engaged in the hole 33, to connect the screw with the plate 31; the contact plate 29 will be connected with the other terminal ol" the coil 19 by the binding screw 88; and the sleeve 26 -will be screwed into the socket 3'? to supp-ort the heater in a vertical position.

To energize the electric heating element it is necessary only to rotate the body to screw the sleeve further into the socket and thereby close the electric circuit in the usual well known manner.

Following is a brief description 'of a typical use ot the heater in the art olf dentistry, for the purpose oit elin'iinating waz; used in the process ot dental inlay work. After preparing a cavity so that a wax form can be taken without distortion a lump oi" plastic war: will be pressed into the cavity to produce the required pattern form; the lump orC wax will then be mounted on av metal sprue former7 one end of which is heated and applied to the lump of wax to form an indentation such that upon the cooling of the wax it will adhere to the sprue former which will then be set in a suitable container, which may be either cylindrical or polygonal, in form; an investment compound preferably consisting of a quick setting mixture ot silex and plaster paris with water, will be poured gently into the container until the investment compound surrounds and covers the was: Storm sui'iiciently. After the investment has hardened it will be placed in the heater and electric current will be applied to energize the resistance element tc produce sutlicient heat to volatilize the wax form and cause its complete absorption by the porous body et the investment; the sprue former will then be removed from the investment and the casting or' the inlay will Vthen proceed in the usual manner.

any other different uses ot the heater will be obvious to skilled users and need not be described here.

i am aware ot the common use oit electric resistance element-s in heaters. I theretore do not claim broadly the use of such elements.

Elaving fully described my invention what l claim as new and desire to secure by Letters Patent is:

l. fin electric heater comprising a hollow body ot insulating and heat-resisting material having a pertorated reduced cylindrical extension and a beveled intermediate part having a series ot openings; a series ot columns lengthwise of and integral with said body and having bevel-ed edges ass ciated to :torni a series ot lengthwise dove-tail grooves in lin-e with the openings through said intern'iediate part on electric resistance element inserted through an opening in said intermediate member and extending lengthwise and downwardly through successive grooves between said columns7 across the upper ends of some columns, and under other columns and constituting entire series oit grooves in the inner wall of the heater and held in place by the beveled edges o1" said columns.

2. An electric heater comprising a hollow body oit insulating and heat-resisting material having lengthwise internal columns with beveled edges associated to 'form dove-tail grooves7 also having a reduced cylindrical section having a central bore and neck provided with a flat shoulder; a continuous electric resistance element held in place by the beveled edges ot said columns; a screw-threaded 'sleeve surrounding said extension and having a central opening and a iiat part engaging on the shoulder ot' said extension to keep the sleeve from rotating on the extension; a lirst contact member on said sleeve electrically connected with one terminal o't said resistance element; a screw extending inwardly through the bore of said extension; and a second contact member electrically connected with said screw and with the other terminal ot said resistance element; to perfect the electric circuit- 3. An insulating structure for electric heaters7 comprising a hollow body of insulating and heat-resisting material having lengthwse internal columns integral with the body7 said columns having beveled edges associated to 'term dove-tail grooves to receive and hold an electric resistance element, some oit said columns having also angular lengthwise grooves adapted to receive an upright polygonal container and keeo it from turning in the body; said body llaving also a radial way to receive a contact plate; said body havingI also a cylindrical sion adapted to support a sleeve pressed thereon; said extension having a vertical bore to receive a. binding screw and having also a neck with a shoulder adapted to prevent rotation of a sleeve. carried by said extension.

4. An electric heater comprising a hollow body of insulating and heat-resisting material having lengthwise internal columns integral with the body, said columns having b-eveled edges associated to form dovetail grooves to receive and hold an electric resistance element, some of said columns having also angular lengthwise grooves to accommodate an upright polygonal container and keep it from turning in the body, said body having also a reduced cylindrical extension having a central bore and a neck provided With a. shoulder; a continuous resistance element held in place by the beveled edges of said columns; a screw-threaded sleeve on the 'extension of said body and having a central opening and a tlat part engaging on said shoulder to keep the sleeve from rotating on the extension; a first contact member on 'said sleeve, electrically connected with one terminal of said resistance element; a 'screw extending inwardly through the of said extension; and a second contact member electrically connect-- ed With said screw1 and With the other terminal o1 said resistance ele-ment to perfect the electric circuit.

Signed at Springield, Sangamon County, Illinois, Nov. lst, 19:24.

JAMES C. DONELAN. Witnesses D. C. JONES, J oHN J. DONELAN. 

